1. Field of the Invention
This invention relates to fan control and more particularly relates to cooling fan control using input power and temperature.
2. Description of the Related Art
Electronic equipment, such as computers, servers, data storage devices, video game consoles, etc., often dissipate a lot power and generate a lot of heat while in operation. Often cooling fans are required to ensure normal equipment operation and to meet reliability goals. Fixed speed fans are sometimes used, however, fixed speed fans are not able to vary the speed of the fan and typically must be designed for worst-case operating conditions. Fixed speed fans are inefficient and undesirable because they run at full capacity at all times. Consequently, fixed speed fans produce more audible noise and diminish fan operating life.
Variable speed fans are commonly used in electronic devices and are capable of varying the speed of the fan. Some variable speed fans can vary fan speed continuously over a range. Other variable speed fans have discrete speeds and may be called multi-speed fans. Multi-speed fans are a step in the right direction toward quieter, more efficient electronic devices, but ultimately may not offer as much efficiency or noise reduction as may be desired. Variable speed fans where the speed is continuously variable over a range are the most flexible type of cooling fans and offer an ability to reduce power consumed by the fan at low speed and can significantly reduce noise of the electronic device that the fan is cooling.
Typically, variable speed fan control is tied to a temperature of a component. The component may be a power supply of an electronic device, a heat generating component in a power supply, a processor, a memory, a hard disk drive, a solid-state drive, etc. in system equipment, and the like. Temperature is typically measured at a desired point and the temperature is used in determining a fan speed. Fan control based on temperature alone, however, is not ideal because the fan speed control is reactive instead of proactive. In other words, adjusting fan speed based on temperature only adjusts the fan speed after the temperature has already increased. Once power dissipation is increased in a component, it takes time for the thermal information being transferred from the heat generating device to reach a temperature sensor. Required cooling sometimes may not be provided before the heat generating device gets too hot. In addition, other components may also be heating up and the heating may not be linear with the component where temperature is sensed.